Periprosthetic infection of metallic implants is one of the most serious complications in orthopedic surgery. (Lynch, et al. 2008 Annual Review of Medicine Vol. 59 415-428; Donlan 2001 Clinical Infectious Diseases 33, 1387-1392; Kurtz, et al. 2008 Journal of Arthroplasty 23, 984-991.) It occurs in 1% to 4% of primary arthroplasties and up to 30% of revision arthroplasties. Patients suffering from periprosthetic infections are often subjected to multiple surgical procedures with variable success rates, with some requiring devastating salvage procedures such as fusion, arthroplasty resection or even amputation. Although microbial contamination of implants can result from a number of causes including insufficient implant sterilization, contamination during the surgical manipulation, direct contact of infected tissue or remote site of infection, biofilm formation surrounding the implant is a common threat making serious local infections both more likely to occur and more difficult to eradicate.
Biofoulant adsorptions on a fouling implant surface provide a conditioning layer for microbial colonization and subsequent formation of biofilms. Bacteria embedded within biofilms can be 2-3 orders of magnitude harder to kill by most antibiotics and biocides, possibly through distinct mechanisms of antimicrobial actions. (Mah, et al. 2003 Nature 426, 306-310.) Treatment of biofilm-mediated infections of orthopedic implants often requires surgical replacement of the contaminated implants along with prolonged antibiotic therapy, which translate into longer hospitalization, higher medical costs, severe functional impairment, morbidity, and increased mortality for patients.
To prevent such devastating events, implant surface modifications aimed at reducing biofouling and attenuating subsequent adverse inflammatory responses and risks for infections have long been sought after. Experiments and theoretic modeling carried out with well-controlled model systems, such as hydrophilic poly(ethylene glycol) (PEG) or zwitterionic self-assembled monolayers formed on atomically flat metal substrates, have elucidated multiple chemical and physical parameters governing the efficiency of anti-fouling including the correlation of the dynamics and structure of interfacial water with non-fouling properties. (Chen, et al. 2010 Polymer 51, 5283-5293.) Clinical translation of these basic findings, however, has been hampered by the topological and compositional complexity of commercial metallic implant surfaces and the sophisticated dynamic tissue environment that cannot be simulated by simple model systems.
Thus, an un-met need continues to exist for viable surface modification strategies that simultaneously and adequately address the anti-fouling and bactericidal needs.